The invention relates to a vacuum pump with at least one rotor shaft having a rotor section with a rotor, a bearing section with a bearing, and a shaft sealing system that is axially situated between the rotor section and the bearing section.
Such vacuum pumps may be configured, among other things, as screw pumps, side channel compressor, and Roots pumps. The mentioned vacuum pumps have in common that they are dry compressing vacuum pumps with oil- or grease-lubricated bearings and/or gears. Typically, these pumps are employed to generate a fore-vacuum. The task of the seal arrangement between the actual rotor and the bearing and the gear, respectively is, on the one hand, avoiding that gas passes from the rotor section to the bearing section and, on the other hand, avoiding that liquid passes from the bearing section into the rotor section. At low rotor speeds and small rotor shaft diameters, relatively good sealing contacting seals can be used, e.g., in the form of radial shaft sealing rings, sliding rings and so forth. At higher rotational speeds and larger rotor shaft diameters, only contactless shaft seals can be used which, however, cannot completely exclude leakages because of their construction.
A known contactless shaft sealing system consists of one or more piston sealing rings as a gas seal and an oil splash ring as an oil seal. They are unable, however, to achieve a reliable and high sealing effect. The gas compressed in the rotor section, however, is not to come into contact with the oil from the bearing section since the oil might be decomposed thereby and thus may lose its oiliness. The leaking oil, gas or gas mixture may also be toxic or explosive and therefore dangerous.
Therefore, it is an object of the invention to improve the shaft seal in a vacuum pump, comprising a gas seal and an oil seal.